docstr: Construct an image path from the image's "index" identifier.
docstr_tok: ["Construct","an","image","path","from","the","image","'s","``","index","''","identifier","."]
code: def image_path_from_index(self, index):
      """
      Construct an image path from the image's "index" identifier.
      """
      image_path = os.path.join(
          self._data_path, "JPEGImages", index + self._image_ext
      )
      assert os.path.exists(
          image_path
      ), "Path does not exist: {}".format(image_path)
      return image_path
  
imports: from __future__ import print_function
  import os, pdb
  import xml.dom.minidom
  import numpy
  import scipy.sparse
  import scipy.io
  import pickle
  import subprocess
  from .imdb import imdb
  from .voc_eval import voc_eval
label_desc: Use image node_id 4 for calling the pascal_voc obj's underlying member method code with example usage: obj.image_path_from_index(index) and returns: image_path